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Color Detection Mechanism Discovered

Researchers at Osaka City University in Japan discovered color detection technique by using the mechanism of pineal organ in zebrafish.

Color vision taking place in eyes is provided by complicated neural mechanism. Scientists from Osaka City University deeply studied ocular color detection of human eye to understand the mechanism involved in color vision. They found color detection with a simple mechanism in the fish pineal organ, an extraocular photosensitive organ on the brain surface. Their findings were published in the journal Proceedings of the National Academy of Sciences on October 15, 2018.

Previously, scientists believed that multiple kinds of color opsins are required to achieve color detection. However, the team at Osaka City University found that a simple technique based on a one type of opsin in a single kind of photoreceptor cell achieves color detection, UV and visible light discrimination, in the fish pineal organ.

The researchers observed that the pineal organ of zebrafish uses a pineal UV-sensitive opsin called as parapinopsin that has a molecular property different from visual opsins in eyes. Using the mechanism of ‘bistable nature’, parapinopsin reverts to the original dark state (inactive state) upon visible light absorption, unlike the pineal and visual opsins, which converts to signaling active photoproduct (light state) upon light absorption.

Akihisa Terakita, professor at the Graduate School of Science at Osaka City University, said: “Environmental light contains all colors of light and its color composition varies depending on time and place. Because two states are photo-interconvertible, the mixture of the two states is formed under natural light. That is, parapinopsin alone behave like two kinds of light sensors.”